Added TROUBLESHOOTING + Debug Info

Issue #34

TROUBLESHOOTING.md

@@ -0,0 +1,15 @@
+If you can't find a solution below, please open an [issue](https://github.com/sendgrid/smtpapi-php/issues).
+
+## Table of Contents
+
+* [Viewing the Request Body](#request-body)
+
+<a name="request-body"></a>
+## Viewing the Request Body
+
+When debugging or testing, it may be useful to examine the raw request body to compare against the [documented format](https://sendgrid.com/docs/API_Reference/SMTP_API/index.html).
+
+In the `examples/example.php` file, after you've added all custom header data, you can do two things:
+
+- Run `var_dump($header);` - Dump out the `Smtpapi\Header` object
+- Run `print $header->jsonString();` to print out a stringified json formatted X-SMTPAPI header